1. Field of the Invention
This invention relates generally to vectorable nozzles and, more particularly, to vectorable axisymmetric variable exhaust nozzles for gas turbine engines.
2. Description of the Prior Art
For military aircraft applications, there exists a need to increase the maneuverability of the aircraft both for air to air combat missions and complicated ground attack missions. Conventionally aerodynamic surfaces such as flaps and aerilons have traditionally been used to effect maneuvers of the aircraft but, depending on the speed and other operating conditions, have limited effectiveness. Modern day aircraft designers are turning to vectorable nozzles which turn or vector the exhaust flow and thrust of the gas turbine engine powering the aircraft. Two dimensional nozzles have been devised which employ relatively flat flaps to direct the pitch or yaw direction of the engine's thrust. However these designs are heavy and require a conversion section to change the axisymmetric flow to a two dimensional flow and still only provides thrust vectoring in one plane, pitch or yaw. Another drawback to the two dimensional nozzle are the flow losses due to the conversion from axisymmetric to 2D flow within the conversion section. In addition to providing thrust vectoring, aircraft engine designers must also allow for nozzle operating conditions which vary significantly during the mission. In order to maintain high performance over the entire operating range of the aircraft, variable exhaust nozzles have been designed which control the opening of the nozzle throat but vectorable nozzles having two dimensional and gimbaling configurations result in increased complexity, weight, cost, and reliability penalties.
Most current multimission aircraft applications employ engines, such as the General Electric F110 engine, with axisymmetric convergent-divergent nozzles to meet operational requirements. Axisymmetric convergent/divergent nozzles have, in serial flow relationship, a convergent section, a throat, and a divergent section. Convergent or primary flaps and divergent or secondary flaps together with associated seals between the flaps define the flow path of their respective sections. Characteristically, these nozzles employ variable area means at both the nozzle throat (at the downstream end of the convergent nozzle) and at the nozzle exit (at the downstream end of the divergent flap). This provides a means to maintain a desired exit to throat area ratio which in turn allows efficient control over the operation of the nozzle. The operation of the nozzle is designed to provide a nozzle throat/exit area ratio schedule which is optimized for the design cycle of the engine and should provide efficient control at both low subsonic and high supersonic flight conditions. These types of nozzles employ circumferentially disposed flaps to produce a generally axisymmetric exhaust flow and use pneumatic or hydraulic actuators to provide the variable operation.
It is therefore highly desirable and an object of the present invention to provide an axisymmetric nozzle vectoring system that can be easily adapted to an existing nozzle design or configuration.
Another object of the present invention is the provision for an axisymmetric variable area exhaust nozzle having thrust vectoring capability in both the pitch and yaw direction.
Yet another object of the present invention to provide an axisymmetric variable area exhaust nozzle having multi-directional thrust vectoring capability which is simple in operation, light in weight, and economical to manufacture.
These objects and other features and advantages will become more readily apparent in the following description when taken in conjunction with the appended drawings.